For all the fabled and rich history of the Academy Awards, the 89th edition of the Oscars will always be remembered for the most astonishing blunder the prestigious ceremony has ever seen.

Hollywood's biggest award night ended with major embarrassment after presenter Warren Beatty and Faye Dunaway wrongly announced La La Land as the winner in the Best Picture category.

PwC, the accountancy firm which has overseen the counting for the Academy Awards ballots for 83 years, subsequently apologised for the fiasco, which was broadcast worldwide, adding it would launch a probe into the causes of the mistake.

At every Oscars ceremony, PwC employees wait offstage and pass envelopes containing the name of the winner for each category but a system which was meant to be foolproof badly malfunctioned.

However, it was not the first time one of the biggest accountancy firms in the world was involved in a debacle. It has been involved in a series of controversies involving a host of firms, such as BHS, Connaught plc, Petrobras and Quinn Insurance – however, these three incidents stand out...

Tesco black hole

In 2015, Tesco ended a 32-year partnership with PwC, which at the time was the longest running of any relationship between a FTSE 100 firm and its accountant, after the Financial Reporting Council launched an investigation into accounting practices at the retailer and the conduct of the accountancy firm in carrying out audits between 2012 and 2014.

The scandal saw almost £2.2bn being wiped off the value of the company's stock-market value, forcing to Tesco to issue a public apology and slashing profit forecast. PwC was subsequently replaced by Deloitte in its role as auditor.

A year earlier, the retailing giant had admitted overstating profits by £263m through misreporting discounts with suppliers among other irregularities. PwC came under scrutiny after it emerged that two members of Tesco's Audit Committee – tasked with monitoring the retailer's relationship with its auditors – had previously worked for the accountancy firm.

The Oscars 2017
26 February 2017: Producer Jordan Horowitz holds up the card for the Best Picture winner "Moonlight." Lucy Nicholson/Reuters

Bank of Tokyo-Mitsubishi UFJ

In 2014, US banking regulators launched a probe into the Japanese lender's role into directing payments for its Iranian customers through its American branch, which contravened US laws. The bank was fined $315m and PwC, which was found guilty of altering an investigation report, received a $25m penalty.

"It is clear that we – as a regulatory community – must work aggressively to reform the cozy relationship between banks and consultants, which far too often has resulted in shoddy work that sweeps wrongdoing under the rug," the New York State Department of Financial Services, Benjamin Lawsky, said.

Lawsky argued Bank of Tokyo had pressured PwC into "water down" and alter the report, which was supposed to be objective.

Tyco settlement

In 2007, PwC paid a $229m settlement after the shareholders of security system firm Tyco International – which has since re-branded as Johnson Controls after a merger – launched a class-action case in the wake of an accounting scandal which rocked the firm in 2002.

Dennis Kozlowski and Mark Swartz, the group's CEO and CFO were found guilty of looting $600m and the former was sentenced to 25 years in jail.

Transneft pipeline case

In 2010, PwC denied any wrongdoing after it was alleged funds were stolen from Transneft, the largest oil pipeline company in the world, during the construction of the East Siberia-Pacific Ocean pipeline.

The project was expected to cost $13bn but, according to a report of the Audit Chamber of the Russian Federation, it was indicated approximately $4bn was siphoned out of the company by employees. PwC was Transneft's auditor but rejected any allegations it was implicated in the incident.

A crumbling Northern Rock

In 2007, the Treasury Select Committee criticised PwC for helping stricken lender Northern Rock, a client of the firm at the time, to sell its mortgage assets while also acting as its auditor.

In 2006, the committee was told that PwC had received £700,000 for writing 10 "comfort letters" (a document assuring the financial solidity, or backing of a company) for Granite.

While PwC earned £1.1m in its role as auditor of Northern Rock, the bank's asset management arm was using securitisation vehicle Granite to parcel up mortgages provided by the bank and sell the value to investors.